Ordinary physical fitness in a muscle is maintained by numerous small contractions and not by violent effort. The latter, if scientifically utilised, can further develop a particular muscle, and can also add to the bulk and strength of any individual muscle group. It is a rare event in daily life to contract the hamstrings to their full extent, and yet their strength and vitality are maintained by the constant contractions and relaxations of small amplitude which they perform in the ordinary process of walking. This illustrates a law of nature which must always be kept in mind when attempting to restore the strength of a weakened muscle.
If a muscle is called upon to perform the full movement of a joint when its power is inadequate to accomplish it, not only will it fail in the attempt, but it will also suffer so severely from fatigue that its efforts in the immediate future will be still further limited. Let us suppose that a patient with a weak deltoid can just raise the extended arm to the horizontal. The performance is gone through with great struggles; and, when completed, the arm drops to the side and prolonged rest is required. If a second attempt is made immediately, the muscle executes a few spasmodic twitches, the arm is elevated only a few degrees and falls helpless to the side again. But if, instead of being told to move the joint through its full range, the patient is instructed to perform the movement up to, say, 15° short of the horizontal, it is probable that it will be carried out five or six times without strain or any need for subsequent rest. It is obvious which of these two methods of exercising the muscle is best calculated to restore its strength. The first law in treatment therefore should be "little and often."
Every muscular contraction that takes place, unless it is purely reflex, entails the use of a large number of nerve elements as well as that of the centre of volition. From the ideational centre an impulse passes to the motor cortex, thence to the medulla, the cord, the anterior horn cells, the nerves, and finally to the neuro-muscular element, which then records the visible result of the impulse in the form of movements of the muscles. In addition, the linking up with the cerebellum controls the movement and co-ordinates it. To secure voluntary movement each link in this chain must be in working order, and it is the masseur's duty to discover if any bar to freedom of movement is due to the weakness of any link.
The highest centre of all, the moral centre, may be at fault and we find the malingerer; the potential of the ideational centre may be lowered as the result of fatigue and we have to deal with a neurasthenic. If this centre is diseased, hysteria or psychasthenia is the cause of the inability to perform voluntary activities. Somewhere lower down there may be a break in the continuity of the chain, and the patient may literally have forgotten how to get the impulse through from brain to muscle. This condition is frequently encountered after prolonged immobilisation, when so-called "sling atrophy" has become an established fact.
The first step in the re-education of such a case as this, or indeed in all cases where muscular disuse is a marked factor in causing disability, is to centre the attention of the patient on one muscle or muscle group. He is told, for instance, to look at his hand, which is held supported before him. The command is next given to raise the hand to the mouth, and instantly the movement is performed quite slowly by the masseur. At first, perhaps, no perceptible contraction will take place in the brachialis anticus, but it is an elastic structure, and the fact of raising the hand must cause the muscle to shorten. The patient is next told to allow the hand to drop on his lap, and it is slowly allowed to do so. The process is repeated three or four times, with a minute's pause for general massage of the arm. Then the patient's attention is called to the brachialis anticus, and while the masseur's one hand controls the movement, the first finger of the other hand taps on the centre of the arm and the order is given to "tighten this muscle" as the hand rises. Presently a twitch will be noticed, and the patient's attention is called to it and he is instructed to do it again. From this point onwards all is plain sailing, but the process of self-suggestion is one which needs to be applied throughout all the earlier stages of treatment. A patient may often appear to be incapable of performing a certain movement, but show him the tendon of the muscle that controls the movement and tell him to make it stand out, or tap on the belly of the muscle and tell him to contract at that point, and quite often the movement will be performed without difficulty. It is often of great assistance to carry out the identical process in the sound limb; in fact, it is often essential.
The great danger in the early stages is to overdo things and try to rush the recovery. Fatigue has the same effect on a weakened muscle that we expect to find when "flogging the tired horse" - both alike suffer severe injury. In prescribing exercises for patients with heart disease, we aim at strengthening the muscles of the heart, and never dream of ordering any movement that might give rise to fatigue. If we do, we know the danger, namely, heart failure: let us beware, then, of fatiguing a weakened skeletal muscle, for assuredly the result will be muscle failure. One of the early symptoms is tremor.
Having made two or three tentative trials to secure contraction, whether success has attended our efforts or no, a few minutes should be spent in massage, and then the process may be repeated. This is called by Lovett the "spacing of exercise," and he has called attention to its supreme importance in the American Journal of the Medical Association, March, 1916.
As soon as voluntary contraction can be secured in response to the word of command, the patient is instructed to contract the muscle twice or three times every hour after treatment. He may only succeed for two or three hours at first and then fail; but with a little perseverance he will be able to perform his exercise right through to the time of the next treatment. Then he is instructed to contract the muscle four, five, or six times at each attempt, and as soon as this can be accomplished he is taught to hold the contraction while he counts three, then while he counts four, five, and six during each contraction.